1. Field of the Invention
The invention relates to an apparatus for a tank system, to a motor vehicle having an apparatus for a tank system and to a method for emptying an activated carbon filter for a tank system.
2. Related Art
A tank system, in particular the tank system of a motor vehicle, usually has an activated carbon filter for filtering volatile fuel components, for example hydrocarbon emissions (HC). Since the activated carbon filter has a particular uptake capacity, it must be regenerated. If the uptake capacity is exceeded, the volatile fuel components pass the activated carbon filter and enter the environment. The activated carbon filter is usually regenerated in the motor vehicle using fresh air during the journey. After the fresh air has flowed through the activated carbon filter, it is supplied to an intake section of an engine. A lambda sensor arranged in the exhaust gas stream of the engine detects the ratio of air to fuel and transmits this ratio to the control device. The hydrocarbon emissions (HC) can be determined from the ratio determined. The control device then regulates the flow of air through the activated carbon filter on the basis of these values.
One disadvantage of this method is the delayed response of the control device. If the motor vehicle is shaken, for example by a curb, a relatively large number of hydrocarbons are emitted in the fuel tank. These hydrocarbons enter the activated carbon filter, which is purged at a constant flow rate. Since the concentration of hydrocarbons in the activated carbon filter has increased but the flow rate remains constant, the concentration of hydrocarbons purged from the activated carbon filter increases. This gas with a higher hydrocarbon concentration is now supplied to the engine. This results in a disturbance in the mixture formation process and thus in a disturbance in the combustion process. The lambda sensor in the exhaust gas stream detects the change in the combustion mixture only after combustion and can then transmit this change to the control device to reduce the flow rate through the activated carbon filter.
A resultant disadvantage is that the flow rate is below the maximum flow rate. If the flow through the activated carbon filter took place at the maximum possible flow rate in this method, this would result in an even more unfavorable mixture formation process in the event of shaking. This may result the mixture no longer being able to be ignited and in the engine stopping.
Another disadvantage of this method is that it is not suitable for motor vehicles having a start/stop function and vehicles with a hybrid drive. This is due to the fact that the regeneration of the activated carbon filter is restricted as a result of the phases in which the engine does not run.